As is generally known, potassium chloride occurs as sylvite. The compound is also known as muriate of potash and can be extracted from salt water. Further methodology to synthesize the compound is by crystallization from solution, electrostatic separation from suitable minerals or flotation.
Other methods for forming potassium chloride include the preparation from solid ore. The ore is exposed to solution stripping and multi-element crystallization. Generally the stripping solution from the rejected liquid, salt and water generated in processing carnallite is selectively stripped the from the solid potassium salt ore to obtain halogen liquid. The liquid is rich in potassium chloride which is subsequently crystallized.
There are innumerable other methods to achieve synthesis, however, these are typically limited in the same manner; expensive unit operations and the inability of the product to be stored without significant moisture absorption.
Kali and Salz Aktiengesellschaft patented a method for manufacturing potassium chloride having a high potassium oxide content (55 wt. %). The precursor was the fine salt resulting from the degradation of carnallite In the process alkyl amine salts are used as conditioning agents and flotation media containing magnesium and potassium chloride are used to separate this fine decomposition salt in an initial flotation stage into a grain size fraction of less than 0.1 mm as a first concentrate and a residue having a grain size of more than 0.315 mm. Subsequent to auxiliary conditioning, the residue is again floated and the potassium chloride surfaces as a second concentrate. The potassium chloride is separated from the mixture without any further conditioning in another flotation stage, and collected.
Ferguson et al., in United States Patent Publication 2005/0036929, published Feb. 17, 2005, disclose an apparatus and method for the production of a compacted potassium chloride granule Essentially, the method includes the use of sodium hexametaphosphate as a binder which is added to the potassium chloride feedstock. The binder is indicated to sequester moisture.
In U.S. Pat. No. 5,503,641, issued Apr. 2, 1996, to Bakardjiev et. al., there is disclosed a process for synthesizing potassium chloride where a multitude of unit operations are required to effect the result. Many of the operations are involved and require high energy expenditures.
Kleine-Kleffmann et al. in U.S. Pat. No. 6,379,414, teach a typical compactor circuit using a known cement of MgCl2 and MgO to harden the mixture. Although the initial flake and pellets are strong, storage is poor as the MgCl2 reacts with moisture in the air to form magnesium chloride hydration complexes and product quality degrades with storage in high humidity.
Dancy et al., in U.S. Pat. No. 4,385,920, provides an agglomeration process that uses a feed stock of SOP or MOP with a size distribution of −80 to +325 mesh with H3PO4 mono or diammonium phosphate with MgO to complete the cement. This is not a compaction process.
In U.S. Pat. No. 5,264,017, Van de Walle, provides an agglomeration process which uses a feed stock of −100 mesh to +325 mesh and MgO and PO4 binder system. This is not a compaction system.
McGough et al., in U.S. Pat. No. 4,428,601, discloses a high grading process for removing NaCl from KCl by dissolving the NaCl in an under saturated brine of NaCl and saturated brine of KCl. This is practiced in all potash mines. The reference does not provide for compaction, agglomeration or granulation.
Having regard to the fact that potassium chloride crystals are very high energy and high stress, dendrites can form between crystals when the same are stored in conditions having relative humidity of greater than approximately 70%. In this manner, the material must be purchased and immediately used in order to avoid particle accretion.
It would be desirable to have a process where the unit operations were minimized with a low energy requirement with the resulting product being resistant to moisture absorption.
The present invention satisfies these goals.